American trypanosomiasis (Chagas disease)

American trypanosomiasis or Chagas disease (CD) is a zoonotic parasitic infection caused by the protozoa Trypanosoma cruzi. It is primarily transmitted by the triatomine bugs (vectorial transmission) or less commonly via blood transfusions, organ transplantation, laboratory accidents, congenitally acquired, or oral transmission (non-vectorial transmission). T. cruzi is endemic only in the Americas from the Southern United States (e.g., Texas, Arizona) to northern Argentina and Chile, excluding all Caribbean islands.

CD has two phases: an acute phase and a chronic phase. During the acute phase, most patients are asymptomatic, but when they show clinical symptoms, it can include inoculation signs (e.g., Romana sign), fever of unknown origin, myocarditis or encephalitis.

If the acute phase is left untreated, patients progress to the chronic phase. During the chronic phase, most patients exhibit no signs or symptoms of CD (indeterminate form), but only 20-30% will exhibit signs of end-organ damage, such as Chagasic cardiomyopathy and/or GI disease (determinate form). This process happens over years to decades.

Only a subset of chronically infected individuals can reactivate under immunosuppressive conditions (e.g., AIDS, organ transplantation). Patients become parasitemic again and behave similarly to those in the acute phase. The most common syndromes per group are as follows:

• Transplant patients → mostly present with myocarditis and panniculitis
• AIDS patients → mostly exhibit meningoencephalitis (resembles acute toxoplasmosis)

During the acute phase, parasites are detectable in blood smears and/or via serum PCR. Conversely, during the chronic phase, parasitemia becomes undetectable and individuals are diagnosed fundamentally via serology. Chronically infected individuals who reactivate, have rising parasitemia and become again detectable in blood smears and/or via serum PCR.

Only two drugs are available for treatment, benznidazole or nifurtimox. Both are poorly tolerated and we recommend you always consult with a specialist, because it can get messy!

As an overview, congenital cases, cases in the acute phase or reactivation, and cases in children less than 18 years of age are always treated. However, it is generally offered to adults less than 50 years of age with NO advanced cardiomyopathy. Once disease has advanced end-organ damage, treatment is only on a case-by-case basis.